Mass violence is arguably the most severe form of disaster affecting the mental health of the largest number of people, thus addressing the mental health needs of victims of mass violence is a major public health challenge. There is a need for delivering effective and early treatments for PTSD to the large number of affected individuals by mass violence. In addition, since there are no randomized controlled trials of mental health treatments for PTSD in survivors of mass violence and disasters, there are no specific evidence-based procedures that can be recommended to meet the special needs of this population. Because resources are often scarce in the aftermath of disasters, a useful intervention is one that is effective, feasible, rapidly available, and efficiently delivered to the largest proportion of affected individuals possible. In terms of treating PTSD in other trauma contexts, there is considerable evidence that cognitive-behavioral therapy (CBT) procedures have substantial success in reducing the array of PTSD symptoms. Overall, the available evidence points to the theoretical and empirical justification for using Prolonged Exposure (PE) and Stress Inoculation Training (SIT), two components of CBT, with patients presenting with PTSD. A practical limitation of available studies is that they are limited to individually administered therapy contexts that typically require between 8 and 12 sessions delivered in a specialty mental health care- setting. The labor-intensive nature of these therapies represents a significant obstacle to provision of therapy to thousands of individuals suffering PTSD in the context of mass violence events. The major aim of this project is to evaluate an abbreviated, primary care-based format of CBT that aims to provide effective self-management skills to individuals with PTSD. The rationale underpinning this intervention is that with appropriate and intensive therapist input during a single session of therapy, supplemented systematically with subsequent self- directed web-based information and guidance for daily homework activity, primary care patients with PTSD stemming from mass violence can benefit from the strategies that have demonstrated efficacy in reducing PTSD symptoms. Survivors of the Pentagon attack on 9/11 will be randomly assigned to PE, SIT, or a supportive counseling control group. Patients' compliance and symptoms will be monitored on the web. Patients will be followed 6 and 12 months post-treatment.